1. Field of the Invention
The present invention relates to a process for producing an article with a microstructure, more particularly to a process which permits production of an article having a microstructure with a relatively complex profile, with a relatively high degree of form accuracy, and with high surface smoothness, and to an article produced by the process.
2. Description of the Related Art
Many methods are available in the art to produce an article, such as a light transmitting plate, having a patterned surface with a relief microstructure. This article is formed using a stamper or a mold having a reversed pattern of the relief microstructure. U.S. Pat. No. 5,776,636 discloses a method for manufacturing light-transmitting plates, which method includes the steps of forming a photo resist layer on a flat substrate, exposing the photo resist so as to form a deflection pattern in the photo resist, developing the exposed photo resist to form a topographical relief in the photo resist corresponding to the deflection pattern, metallizing and electro forming the surface of the photo resist to thereby form a stamper, and injection molding the light-transmitting plate using the stamper. It is possible to expose the deflection pattern using parallel light beams irradiated on the photo resist layer through an over-laid photo mask. In this case, the sectional configuration of the topographical relief is usually rectangular or trapezoidal. It is also possible to directly draw the pattern on the photo resist using an optical beam. In this case, the configuration of the topographical relief can be modified by adjusting exposure conditions and/or by adding a baking step between the developing and metallizing steps. This results in added procedures in the manufacturing process of the light transmitting plate. Moreover, it is difficult in the aforementioned method to form a topographical relief with a complex profile and with high surface smoothness and a relatively high degree of form accuracy.
Therefore, the main object of the present invention is to provide to a process for producing an article with a microstructure having a relatively complex microstructure pattern and high surface smoothness and at a relatively high degree of form accuracy, and to an article produced by the process.
Accordingly, the process of the present invention includes the steps of forming a primary relief structure on a surface of a substrate, applying a photo resist onthe substrate, exposing part of the photo resist using a photo mask so as to form a microstructure pattern, developing the microstructure pattern in the exposed photo resist, thereby allowing access to a part of the primary relief structure from the photo resist, and thereby forming a patterned surface with a microstructure relief that is bounded by the exposed part of the primary relief structure and by remainder of the photo resist on the substrate, and forming a metal layer on the patterned surface to form the article having the microstructure with a profile corresponding to the microstructure relief on the patterned surface.